package app

import (
	"context"
	"fmt"
	"os"
	"strings"

	"gitea.maximumdirect.net/eric/narratio/internal/adapters/storage"
	"gitea.maximumdirect.net/eric/narratio/internal/artifacts"
	"gitea.maximumdirect.net/eric/narratio/internal/config"
	"gitea.maximumdirect.net/eric/narratio/internal/manifest"
)

// RemoteCurrentState captures discovered committed remote archive state for one session.
type RemoteCurrentState struct {
	Bucket             string
	SessionPrefix      string
	CurrentRunIDKey    string
	CurrentManifestKey string
	RunID              string
	SessionID          string
	Campaign           string
	Manifest           *manifest.Manifest
}

func discoverRemoteCurrentState(ctx context.Context, cfg *config.Config, store storage.ObjectStore) (*RemoteCurrentState, error) {
	if cfg == nil || cfg.Pipeline == nil || cfg.Session == nil {
		return nil, fmt.Errorf("resolved config with pipeline/session is required")
	}
	if store == nil {
		return nil, fmt.Errorf("remote object store is required")
	}

	bucket := artifacts.ResolveArchiveBucket(cfg, nil)
	if strings.TrimSpace(bucket) == "" {
		return nil, fmt.Errorf("archive bucket is required")
	}
	sessionPrefix, err := artifacts.ResolveArchiveSessionPrefix(cfg, nil)
	if err != nil {
		return nil, fmt.Errorf("resolve archive session prefix: %w", err)
	}
	currentManifestKey, currentRunIDKey := artifacts.ResolveArchiveCurrentStateKeys(sessionPrefix)

	exists, err := store.Exists(ctx, currentRunIDKey)
	if err != nil {
		return nil, fmt.Errorf("check remote current run pointer %q: %w", currentRunIDKey, err)
	}
	if !exists {
		return nil, fmt.Errorf("remote current run pointer missing: %q", currentRunIDKey)
	}

	runIDPath, err := downloadObjectToTemp(ctx, store, currentRunIDKey, "narratio-restore-current-run-id-*.txt")
	if err != nil {
		return nil, fmt.Errorf("download remote current run pointer %q: %w", currentRunIDKey, err)
	}
	defer func() { _ = os.Remove(runIDPath) }()

	runIDData, err := os.ReadFile(runIDPath)
	if err != nil {
		return nil, fmt.Errorf("read downloaded run pointer %q: %w", currentRunIDKey, err)
	}
	runID := strings.TrimSpace(string(runIDData))
	if runID == "" {
		return nil, fmt.Errorf("remote current run pointer %q is empty", currentRunIDKey)
	}

	exists, err = store.Exists(ctx, currentManifestKey)
	if err != nil {
		return nil, fmt.Errorf("check remote current manifest %q: %w", currentManifestKey, err)
	}
	if !exists {
		return nil, fmt.Errorf("remote current manifest missing: %q", currentManifestKey)
	}

	manifestPath, err := downloadObjectToTemp(ctx, store, currentManifestKey, "narratio-restore-current-manifest-*.json")
	if err != nil {
		return nil, fmt.Errorf("download remote current manifest %q: %w", currentManifestKey, err)
	}
	defer func() { _ = os.Remove(manifestPath) }()

	manifestStore := &manifest.LocalStore{}
	remoteManifest, err := manifestStore.Load(ctx, manifestPath)
	if err != nil {
		return nil, fmt.Errorf("remote current manifest decode failed: %w", err)
	}

	requestedSession := strings.TrimSpace(cfg.Session.SessionID)
	requestedCampaign := strings.TrimSpace(cfg.Session.Campaign)
	manifestSession := strings.TrimSpace(remoteManifest.SessionID)
	manifestCampaign := strings.TrimSpace(remoteManifest.Campaign)

	if manifestSession != requestedSession {
		return nil, fmt.Errorf(
			"remote current manifest session_id %q does not match requested session_id %q",
			manifestSession,
			requestedSession,
		)
	}
	if manifestCampaign == "" {
		return nil, fmt.Errorf("remote current manifest campaign is required")
	}
	if manifestCampaign != requestedCampaign {
		return nil, fmt.Errorf(
			"remote current manifest campaign %q does not match requested campaign %q",
			manifestCampaign,
			requestedCampaign,
		)
	}

	return &RemoteCurrentState{
		Bucket:             bucket,
		SessionPrefix:      sessionPrefix,
		CurrentRunIDKey:    currentRunIDKey,
		CurrentManifestKey: currentManifestKey,
		RunID:              runID,
		SessionID:          manifestSession,
		Campaign:           manifestCampaign,
		Manifest:           remoteManifest,
	}, nil
}

func downloadObjectToTemp(ctx context.Context, store storage.ObjectStore, key, pattern string) (string, error) {
	tmp, err := os.CreateTemp("", pattern)
	if err != nil {
		return "", fmt.Errorf("create temp file: %w", err)
	}
	path := tmp.Name()
	if err := tmp.Close(); err != nil {
		_ = os.Remove(path)
		return "", fmt.Errorf("close temp file: %w", err)
	}

	if err := store.Download(ctx, key, path); err != nil {
		_ = os.Remove(path)
		return "", err
	}
	return path, nil
}